This invention relates to a dual-section oil-filled AC capacitor package and more particularly to such a package of oval-cylindrical shape having a high packing density and low cost. The invention is even more specifically directed to dual AC capacitors wherein the ratio of capacitances is greater than unity and usually from about 3 to 12. Such capacitors are especially suitable for incorporation in air-conditioners.
Air conditioners typically employ a compressor-motor-run capacitor and a fan-motor-run capacitor having the above noted relative values. The two run capacitors are typically of the oil filled type and are provided in the same package to save space and weight. The corresponding motor-start capacitors are more than an order of magnitude larger in capacitance and normally are an electrolytic type, not includable in the same package with the motor run capacitors.
An earlier oval AC capacitor package containing a single capacitor section typically employed a wound-foil-oil-filled type section having been flattened to snugly fit the oval can. It has more recently been the practice by a number of air conditioner manufacturers to use an oval dual capacitor that includes a small diameter section for the fan-run capacitor and a large diameter section for the compressor-run capacitor, both sections having a circular-cylindrical shape, i.e. not flattened. Such a construction, however, provides a low packing density even though in the newer capacitors, there is substituted a metallized polypropylene sheet for the bulkier foil of earlier AC capacitors. The low packing density of that oval package, having two round sections of disparate diameters, is typically not less than 20% in cost or weight compared with two discrete AC capacitors. For these reasons, dual AC capacitors have found limited use in the highly standardized air conditioning industry.
For both single capacitor and dual capacitors used in the motor-run circuits, the industry has invested heavily in tooling that commits them to the use of AC capacitors packaged in an oval-cylindrical can. Those oval cans accommodate two circular-cylindrical capacitor sections side-by-side. The commitment to oval cans was made more than a decade ago.
Further illustrating industry commitment to oval packages, there has been available a circular-cylindrical dual-AC-capacitor package, described by Sherry in the U.K. Patent Application GB No. 2,089,569 A, published June 23, 1982 and assigned to the same assignee as is the present invention. It includes a single round section having a pair of co-wound metal films, one of which serves as a common electrode and the other of which is open in a middle region to provide the two other electrodes of the two capacitors. The single round section fits snugly in a circular-cylindrical can. A major advantage of this high-density package is that the capacitor section occupies almost all of the can, requiring therefore a minimum of the expensive dielectric oil and also leading to a package having a relatively low weight. Unfortunately, as noted above, the major users demand an oval package that is physically compatable with air conditioners made many years ago and those of similar design being manufactured currently.
It is an object of this invention to provide an oval dual-AC-capacitor package having a high packing efficiency and low cost.
It is a further object of this invention to provide such a capacitor wherein the ratio of the two capacities is greater than 1 and less than 12.